Otto Preminger’s weird black comedy-mystery, with a wonderful cast of eccentrics, filmed on location around London. Plans for a 2007 remake with Reese Witherspoon, fell through when she backed out, and the project seems to have been forgotten.

The glorious art nouveau pub, to which Newhouse takes the distraught Ann for a drink, is the remarkable Warrington, 93 Warrington Crescent, Maida Vale. Overblown crimson and gilt, the Warrington could be the anteroom of a Parisian bordello, and rumours persist that, indeed, you could once have been ‘entertained’ in its private rooms. Certainly, music hall star Marie Lloyd enjoyed quaffing Champers in the theatrical ambience.

The Warrington’s upstairs dining room was renovated to house a new Gordon Ramsay restaurant. The story goes that the sweary TV chef was in the area to view the nearby closed Crocker’s Folly (a magnificent pub, itself a film location for Warren Beatty’s Reds and Oliver Parker’s The Importance of Being Earnest), stopped by the Warrington for a drink, and promptly bought that instead. In 2011, the pub was sold to the Faucett Inn chain.

Don’t be fooled by the ‘Frognal End, NW3’ street signs – there’s no such place. The mansion belonging to Ann’s brother, Stephen (2001’s astronaut Keir Dullea), where the mystery is finally unravelled, is Cannon Hall, 14 Cannon Place at Squire’s Mount tucked away off East Heath Road, NW3, just off Hampstead Heath, once the home of actor-manager Gerald du Maurier – and father of Daphne du Maurier, author of Rebecca, Jamaica Inn, The Birds and Don’t Look Now (tube: Hampstead, Northern Line).